1. Field of the Invention
This invention relates to a process for isomerization of lower-polymers of butadiene which comprises treating a lower polymer of butadiene or a lower copolymer of butadiene with a combination catalyst comprising an organic alkali metal compound and a diamine compound to thereby isomerize a non-conjugated double bond in the polymer to a conjugated double bond.
And further, it relates to a process for producing an isomerized butadine lower polymer having conjugated double bonds which comprises performing a lower polymerization and copolymerization of butadiene with an organic alkali metal catalyst or alkali metal, followed by a further reaction with an addition of a diamine compound to the reaction mixture in situ to isomerize their non-conjugated double bond to the conjugated double bond.
2. Description of the Prior Art
It is known that a lower polymer or copolymer of butadiene can be prepared by polymerizing butadiene or copolymerizing it with another monomer in the presence of a catalyst comprising an alkali metal catalyst, an organic alkali metal catalyst or a combination catalyst comprising a compound of a metal belonging to Group VIII of the periodic Table and an alkyl aluminum halogenide.
And there are also many published reports with regard to the production of lower polymers of butadiene and copolymers of butadiene with conjugated diolefines or vinyl-substituted aromatic compounds using organic alkali metals or alkali metal dispersions as a component of the catalyst. Some of the typical catalysts used in the production are, for example, a metallic sodium dispersion-naphthalene complex (Japanese Patent Publication No. 7051/65, 27432/68), a metallic sodium-ether complex and an organolithium compound (Japanese Patent Publication No. 26477/66, U.S. Pat. Nos. 2,913,444, 3,097,108, 3,105,828, 3,119,800 and 3,140,278: a living polymerization in tetrahydrofuran solvent). And a chain transfer polymerization process (Japanese Patent Publication No. 7446/57), which comprises employing aromatic hydrocarbons such as toluene or xylene as a chain transfer agent with the addition of dioxane and isopropyl alcohol, etc. to metallic sodium dispersions.
Since a lower polymer or copolymer of butadiene obtained by such known method has a large amount of 1,2-double bonds and 1,4-double bonds in the molecule and has a relatively high reactivity, the polymer is used in various fields as a paint vehicle, thermosetting resin, adhesive, rubber compounding material, intermediate material for various synthetic reactions and prepolymer. However, since the double bonds of such lower polymer of butadiene are non-conjugated ones, it is still insufficient with respect to the reactivity as compared with compounds containing conjugated double bonds in the molecule such as tung oil and dehydrated castor oil. Accordingly, it is expected that if non-conjugated double bonds of the butadiene units contained in a lower polymer or copolymer of butadiene can be isomerized to conjugated double bonds by an economically advantageous method to thereby improve the reactivity of the lower polymer of butadiene, its application fields will be further expanded.
As an instance of such isomerization method, there is known a method comprising reacting a lower polymer of butadiene at 110.degree. to 250.degree. C, in the presence of a catalyst comprising a compound of a transition metal belonging to Group VIII of the Periodic Table (Japanese Patent Publication No. 5757/68). This method, however, is defective in that the reaction should be conducted at high temperatures and such undesired phenomena as gelation and coloration of the polymer are readily caused to occur. Further, the catalyst comprising a compound of a transition metal belonging to Group VIII of the Periodic Table is expensive, and therefore, this method is disadvantageous from the economical viewpoint.
A method comprising subjecting a lower polymer of butadiene to air oxidation in the presence of a cobalt naphthenate catalyst to thereby improve the reactivity of the lower polymer is also known in the art (Japanese Patent Publications No. 4592/58 and No. 3865/71).
Moreover, in order to commercialize these butadiene lower polymers and copolymers, it will be required that they are isomerized further in their separate ways, and this will result in the increase of production costs. However, according to this method, the amount of the conjugated diene formed by the reaction is very small, and coloration or degradation is readily caused to occur.